Somewhere in the deep, dark corner of a neuroscience lab, willing subjects are having magnetic pulses applied to their heads. Or electrodes plastered to their skulls, allowing an electrical current to run between brain areas. Why? Techniques such as transcranial magnetic stimulation (TMS) – in which an electric coil held over the head applies magnetic pulses to create currents in the brain – and transcranial direct current stimulation (tDCS) – which delivers a low, continuous electrical current to the brain through electrodes attached to the head – were developed to allow researchers to stimulate or inhibit firing in the human brain non-invasively. TMS and tDCS have been used to study how currents and magnets can increase cognitive function and motor skills; for example, to recover motor function after a stroke or reduce fatigue in MS patients.
Inevitably, when you introduce a new gadget for the betterment of humanity, your average Joe will start to wonder, “What other fun thing can I use this for? ” Or in the case of your average overachieving triathlete, “Can I take this and use it to make myself better/smarter/faster?”
This is what’s happening with TMS and tDCS — can we in fact use it to make ourselves better/smarter/faster human beings?” And, if this is the case, as athletes – should we? Let’s take a look.
What Does the Science Say?
In a recently published study, participants were faced with a hand grip task where on each trial, they had the option of repeating a specified, difficult grip intensity (for reward) or quitting. “Effort perception” was assessed a few different ways – researchers had subjects self-rate their perceived exertion, and also factored in subjects’ acceptance rate (choosing to squeeze rather than bail on a trial), accuracy of repeating an effort, influence of the previous trial’s effort on the current trial, and pupil dilation (physiology fact of the day – your pupils dilate in response to stress/physical effort). In other words, they covered all their bases here. What they found was that by using TMS stimulation to disrupt activity in a particular area of the brain called the supplementary motor area, they could actually decrease subjects’ effort perception during the grip task.
It also appears that if you’re an athlete, you may be able to favorably manipulate your heart rate variability (HRV) with brain stim: applying tDCS over the left temporal cortex increased HRV in highly fit subjects (male national road race cyclist competitors, N = 20). Note that this was at rest, the effect was not seen in non-athletes (a discussion for a different day), and no effects were seen with sham stimulation (so this wasn’t a placebo effect). Why does manipulating HRV matter? The improvements here reflect a better balance of sympathetic/parasympathetic nervous system activity, which is related to how well you’ll bounce back from stress, including recovery from training sessions.
In a similar study, tDCS over temporal cortex (or sham stimulation) was applied prior to a ramp test in 10 trained cyclists. When the cyclists received 20 minutes of tDCS first, they showed about 4% greater peak power output, lower heart rate while at sub-maximal wattage, and a slower increase in perceived exertion. However, maximum perceived exertion and heart rate weren’t affected. With only 10 subjects, hard to say how much we should believe these effects, but this study at least gives us a hint that messing with the brain’s perception of effort like this could translate into better athletic performance – here, on cycling max efforts.
Sum: we can affect how hard physical effort feels, nervous system activity balance, and possibly how much power you can output on a bike by disrupting activity in brain areas responsible for motor and autonomic nervous system control.
… What’s to stop me from going on eBay right now, buying a magnet or some powerful electrodes, attaching them to my skull, and blasting my motor neurons into oblivion?
Nothing. I’m sure some overly-enthusiastic amateurs have already done this. But there are quite a few things to figure out before we can use brain stimulation to gain an actual athletic advantage. Most obviously, we’ve yet to see consistent, convincing evidence that brain stim translates into significant performance gains. Most importantly, localization and safety: it’s relatively difficult to accurately position your electrodes/coil to stimulate the right brain area without knowing your own anatomy. The best way to TMS or tDCS your brain is with a localizing MRI first. My supplementary motor area might be 3mm further back on my skull than yours, and that may mean the difference between seeing a performance effect and seeing nothing. And although TMS and tDCS have been used for years now, there still isn’t “long-term” data on side effects.
Although the science is exciting and the logic is sound, there are still many open questions – e.g., who will the “high responders” be, and why – elites versus non-elites? Does concurrent stimulation + physical training have an additive effect, versus stim pre-exercise? What are the minimal and maximal effective doses?
And…what happens when you do this pre-competition? Are you essentially doping your brain by using a device to physically alter its electrical activity, and should such “neuro-doping” be banned? And in that case, how could you possibly monitor illegal use?
I have no idea, but it will be interesting to see where this goes as the science progresses. “At home” tDCS kits are already out there, and at some point in the not-too-distant future – likely when we figure out how big the performance gains actually are, and how one can go about getting those gains – whether or not this neuro-doping violates “the spirit of the sport” will need to be addressed. In the meantime, I’m going to hold off on the electrodes. Too busy sitting in my altitude tent, drinking my beet juice anyways…